Here's why:
* Genres are not proper nouns: Genres like "science fiction," "romance," or "horror" are not specific names of people, places, or things. They are general categories, and lowercase is the standard for general terms.
Example:
* Incorrect: I love reading science fiction, but I also enjoy some fantasy.
* Correct: I love reading science fiction, but I also enjoy some fantasy.
Exceptions:
* At the beginning of a sentence: You would capitalize a genre at the beginning of a sentence, just like any other word.
* Formal titles: If a genre is part of a formal title, it would be capitalized. For example: "The Encyclopedia of Science Fiction."
Let me know if you have any other questions about capitalization!